Predictions measuring the effects of global warming on Australia assert that global warming will negatively impact the continent's environment, economy, and communities. Australia is vulnerable to the effects of global warming projected for the next 50 to 100 years because of its extensive arid and semi-arid areas, an already warm climate, high annual rainfall variability, and existing pressures on water supply. The continent's high fire risk increases this susceptibility to change in temperature and climate. Additionally, Australia's population is highly concentrated in coastal areas, and its important tourism industry depends on the health of the Great Barrier Reef and other fragile ecosystems. The impacts of climate change in Australia will be complex and to some degree uncertain, but increased foresight may enable the country to safeguard its future through planned mitigation and adaptation. Mitigation may reduce the ultimate extent of climate change and its impacts, but requires global solutions and cooperation, while adaptation can be performed at national and local levels.[1]

Analysis of future emissions trajectories indicates that, left unchecked, human emissions of greenhouse gases (GHG) will increase several fold during the 21st century. Consequently, Australia's annual average temperatures are projected to increase 0.4–2.0 °C above 1990 levels by the year 2030, and 1–6 °C by 2070. Average precipitation in southwest and southeast Australia is projected to decline during this time period, while regions such as the northwest may experience increases in rainfall. Meanwhile, Australia's coastlines will experience erosion and inundation from an estimated 8–88 cm increase in global sea level. Such changes in climate will have diverse implications for Australia's environment, economy, and public health.[2]

A 2007 technical report on climate change in Australia jointly published by Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Bureau of Meteorology provided climate change projections accounting for a number of variables, including temperature, rainfall, and others. The report provided assessments of observed Australian climate changes and causes, and projections for 2030 and 2070, under a range of emissions scenarios.[3]

The Government of Australia acknowledges the impacts of changing climatic conditions, and its Department of Climate Change and Energy Efficiency has established the Australian Climate Change Science Program (ACCSP), which aims to understand the causes, nature, timing, and consequences of climate change so as to inform the Australian response. The ACCSP will dedicate $14.4 million per year towards climate change research and has already made substantial progress with a recent publication, Australian Climate Change Research: Perspectives on Successes, Challenges, and Future Directions.

Climate change is expected to increase the frequency and intensity of bushfires.

Firefighting officials are concerned that the effects climate change will increase the frequency and intensity of bushfires under even a "low global warming" scenario.[4] A 2006 report, prepared by CSIRO Marine and Atmospheric Research, Bushfire CRC, and the Australian Bureau of Meteorology, identified South Eastern Australia as one of the 3 most fire-prone areas in the world,[5] and concluded that an increase in fire-weather risk is likely at most sites over the next several decades, including the average number of days when the McArthur Forest Fire Danger Index rating is very high or extreme. It also found that the combined frequencies of days with very high and extreme FFDI ratings are likely to increase 4–25% by 2020 and 15–70% by 2050, and that the increase in fire-weather risk is generally largest inland.[6]

In 2009, the Black Saturday bushfires erupted after a period of record hot weather resulting in the loss of 173 lives [7]
and the destruction of 1830 homes, and the newly found homelessness of over 7,000 people.[8]

Australian Greens leader Bob Brown said that the fires were "a sobering reminder of the need for this nation and the whole world to act and put at a priority the need to tackle climate change".[9] The Black Saturday Royal Commission recommended that "the amount of fuel-reduction burning done on public land each year should be more than doubled".[7]

In 2018, the fire season in Australia began in the winter. August 2018 is hotter and more windy than the average. Those meteorologic conditions led to a drought in New South Wales. The Government of the state already give more than $1 billion to help the farmers. The hotter and drier climate led to more fires. The fire seasons in Australia are lengthening and fire events became more frequent in the latest 30 years. These trends are probably linked to climate change.[10][11]

Globally, the World Meteorological Organization has claimed that extreme weather events are on the rise as a result of human interference in the climate system,[12] and climate models indicate the potential for increases in extremes of temperature, precipitation, droughts, storms, and floods.[13] The CSIRO predicts that a temperature rise of between 2 and 3 degrees Celsius on the Australian continent could incur some of the following extreme weather occurrences, in addition to standard patterns:

In 100 years, strong tides would increase by 12–16% along eastern Victoria's coast.[15]

The forest fire danger indices in New South Wales and Western Australia would grow by 10% and the forest fire danger indices in south, central and north-east Australia would increase by more than 10%.[16][17]

There are a number of issues that could cause a range of direct and indirect consequences to many regions of the world, including Australia. These include large-scale singularities – sudden, potentially disastrous changes in ecosystems brought on gradual changes.[18] The collapse of regional, or even global, coral reef ecosystems is possibly the most significant potential large-scale singularity to Australia. Coral reef ecosystems have a narrow temperature range, meaning that they can rapidly change from being a healthy system to being stressed, bleached, or at worst, eradicated.[19]

Ecosystem changes in other parts of the world could also have serious consequences for climate change for the Australian continent. Evidence from carbon cycle modeling suggests that the deaths of forests in tropical regions might increase the net concentration of carbon dioxide in the atmosphere, by converting the terrestrial biosphere from a carbon sink to a source of CO2.[20]

Recently, scientists have expressed concern about the potential for climate change to destabilize the Greenland ice sheet and West Antarctic Ice Sheet.[21] An increase in global temperatures as well as the melting of glaciers and ice sheets (which causes an increase in the volume of freshwater flowing into the ocean), could threaten the balance of the global ocean thermohaline circulation (THC). Such deterioration could cause significant environmental and economic consequences through regional climate shifts in Australia and elsewhere, resulting from change in the global ocean circulation.[22][23] Melting of glaciers and ice sheets also contributes to sea-level rise. Immense quantities of ice are held in the ice sheets of West Antarctica and Greenland, jointly containing the equivalent of approximately 12 meters of sea-level rise. Deterioration or breakdown of these ice sheets would lead to irreversible sea-level rise and coastal inundation across the globe.

The CSIRO predicts that additional singularities caused by a temperature rise of between 2 and 3 degrees Celsius will be:

Australia has some of the world's most diverse ecosystems and natural habitats, and it may be this variety that makes them the Earth's most fragile and at-risk when exposed to climate change. The Great Barrier Reef is a prime example. Over the past 20 years it has experienced unparalleled rates of bleaching. Additional warming of 1 °C is expected to cause substantial losses of species and of associated coral communities.[2]

The CSIRO predicts that the additional results in Australia of a temperature rise of between 2 and 3 degrees Celsius will be:

Small changes caused by global warming, such as a longer growing season, a more temperate climate and increased CO2 concentrations, may benefit Australian crop agriculture and forestry in the short term. However, such benefits are unlikely to be sustained with increasingly severe effects of global warming. Changes in precipitation and consequent water management problems will further exacerbate Australia's current water availability and quality challenges, both for commercial and residential use.[2]

The CSIRO predicts that the additional results in Australia of a temperature rise of between 3 and 4 degrees Celsius will be:

Healthy and diverse vegetation is essential to river health and quality, and many of Australia's most important catchments are covered by native forest, maintaining a healthy ecosystem. Climate change will affect growth, species composition and pest incursion of native species and in turn will profoundly affect water supply from these catchments. Increased re-afforestation in cleared catchments also has the prospect for water losses.[38]

The CSIRO predicts that the additional results in Australia of a temperature rise of between only 1 and 2 degrees Celsius will be:

Global warming could lead to substantial alterations in climate extremes, such as tropical cyclones, heat waves and severe precipitation events. This would degrade infrastructure and rise costs through intensified energy demands, maintenance for damaged transportation infrastructure, and disasters, such as coastal flooding.[2]:5 In the coastal zone, sea level rise and storm surge may be more critical drivers of these changes than either temperature or precipitation.[2]:20

The CSIRO describes the additional impact on settlements and infrastructure for rises in temperature of only 1 to 2 degrees Celsius:

A 22% rise in 100-year storm surge height around Cairns; as a result the area flooded doubles.[14]

A 1% decrease in peak electricity demands in Melbourne and Sydney.[42][43]

Climate change will have a higher impact on Australia's coastal communities, due to the concentration of population, commerce and industry. Climate modelling suggests that a temperature rise of 1–2 °C will result in more intense storm winds, including those from tropical cyclones.[44] Combine this with sea level rise, and the result is greater flooding, due to higher levels of storm surge and wind speed.Coleman, T. (2002) The impact of climate change on insurance against catastrophes. Proceedings of Living with Climate Change Conference. Canberra, 19 December.) Tourism of coastal areas may also be affected by coastal inundation and beach erosion, as a result of sea level rise and storm events. At higher levels of warming, coastal impacts become more severe with higher storm winds and sea levels.

A report released in October 2009 by the Standing Committee on Climate Change, Water, Environment and the arts, studying the effects of a 1-metre sea level rise, possible within the next 30–60 years, concluded that around 700,000 properties around Australia, including 80,000 buildings, would be inundated. The collective value of these properties is estimated at $150 billion.[45]

A 1-metre sea level rise would have massive impacts, not just on property and associated economic systems, but in displacement of human populations throughout the continent. Queensland is the state most at risk due to the presence of valuable beachfront housing.[46]

Adelaide's Hills Face Zone (HFZ) is a steep and rugged escarpment created by the Eden–Burnside Fault, forming the western boundary of the Adelaide Hills. The HFZ contains a number of conservation parks such as Morialta CP and Cleland CP, which support large areas of fire-prone vegetation. The escarpment is cut by a number of very rugged gorges such as the Morialtta Gorge and Waterfall Gully. Development is restricted in the HFZ, with settlement mainly occurring on the uplands east of the escarpment. The roads traversing the escarpment tend to be very narrow and winding, and access or escape routes to some areas of settlement is poor, a factor which affected suburbs such as Greenhill during the 1980 Ash Wednesday bushfires.

The threat of bushfires is very prevalent within the region[47] and poses the threat of spreading into adjacent populated areas.[48]

Many suburbs of Melbourne are situated around Port Phillip. A sea level rise of 1 m would threaten the surrounding area, including suburban communities. It would also flood all of the city's major cargo shipping docks, surrounding cargo storage areas, the Docklands development and several marinas and berths in Port Phillip. A sea level rise of 1 m would displace around 5–10,000 people and directly impact approximately 60–80,000 people in metropolitan Melbourne/Mornington Peninsula alone.

A sea level rise of 5–10 m would see the CBD at the mouth of the Yarra River and former wetlands entirely flooded, bringing the shoreline back to towns and suburbs such as Kensington, Footscray, Altona North, Prahran, Elsternwick, Dingley, Dandenong South, Pakenham South, Laverton and Lara. Areas completely inundated would include much of the Bellarine Peninsula and Swan Island, parts of Geelong, the Werribee Treatment Plant, all of Altona, Point Cook, Williamstown, West Melbourne, Port Melbourne, South Melbourne, Elwood, Mordialloc, Braeside, Aspendale, Edithvale, Chelsea, Bonbeach, Carrum, Patterson Lakes, Seaford, Frankston North, Safety Beach and parts of Dromana, Rosebud, Rye, Blairgowrie and Sorrento.

A rise of 5–10 m would also disrupt agriculture to the west of Port Phillip and around Geelong, increase the width of the Yarra River back to Hawthorn and the Maribyrnong River back to Avondale Heights. In addition, the MCG would be located precariously close to the wider Yarra River and be subject to flooding. Such a rise would displace roughly 200,000 people in metropolitan Melbourne and the Mornington Peninsula, excluding Geelong and the Bellarine Peninsula.

A sea level rise of 1 m would affect roadways near the coast and pose a threat to the Stony Point rail line and West Melbourne dock and cargo lines and yards. Whilst a rise of 5–10 m would cut rail transport among the CBD and the western suburbs and between Melbourne and Geelong. Rail & freeway transportation to the Mornington Peninsula would also be cut off. The rise would submerge the West Gate Freeway, CityLink tunnels, and the northern link of CityLink, rendering the West Gate and Bolte Bridges useless. Bridges over the Yarra & Maribyrnong in the CBD and inner Melbourne would be submerged.

A sea water rise of 1.1 m would inundate eight to eleven thousand residential buildings in Tasmania, more than 2500 of those in the Clarence and Kingbourgh local government areas, which are part of Greater Hobart.[50]

The Port of Brisbane and Brisbane Airport would be at risk of inundation from a 1-m rise. A sea level rise of 10 m would almost completely flood Bribie Island. The Gold Coast, being built on low-lying land, particularly parts that were formerly wetlands, including many canal developments, are particularly at risk. A sea level rise of 10 m would completely inundate the Gold Coast.

The Great Barrier Reef could be killed as a result of the rise in water temperature forecast by the IPCC. A UNESCOWorld Heritage Site, the reef has experienced unprecedented rates of bleaching over the past two decades, and additional warming of only 1 °C is anticipated to cause considerable losses or contractions of species associated with coral communities.[2]

The coral reefs of the World Heritage-listed Lord Howe Island could be killed as a result of the rise in water temperature forecast by the IPCC.[51]
As of April 2019, approximately 5% of the coral is dead.[52]

^Howden, S.M., and Crimp, S. (2001) Effect of climate and climate change on electricity demand in Australia. In: Integrating Models for Natural Resources Management Across Disciplines, Issues and Scales. Proceedings of the International Congress on Modelling and Simulation, December 2001, Canberra.